The original Hebrew is somewhat ambiguous in its formulation. Literally, it says, And the Lord raised up a saviour for the Israelites—and he saved them—Othniel the Kenizzite.
So who saved Israel? The implication from the central position of and he saved them
is: both. Othniel was involved in saving Israel, but in an ultimate way, the Lord accomplished this through Othniel. The emphasis on this clause is only heightened when it is noted that in the Hebrew, precisely eight lines precede the clause and eight lines follow it. Othniel works so in tandem with Yahweh that they merge together as one.
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9 But when the people of Israel cried out to the LORD, the LORD raised up a deliverer for the people of Israel, who saved them, Othniel the son of Kenaz, Caleb’s younger brother.